Deck 6: Cultivating Microorganisms

Question 1

Which one of the following is NOT a physical factor that affects the growth rate of cells?

A) nutrient concentration
B) temperature
C) pressure
D) light intensity
E) radiation

Answer 1

A

Question 2

What is nitrogen fixation?

A) The oxidation of nitrate to ammonia for assimilation.
B) The oxidation of ammonia to nitrate for assimilation.
C) The reduction of dinitrogen to ammonia for assimilation.
D) The reduction of nitrate to dinitrogen for assimilation.
E) The release of an amino group from an amino acid for assimilation.

Answer 2

C

Question 3

A heterotroph is defined as an organism that uses _____ as a source of _____.

A) sunlight; energy
B) organic compounds; carbon
C) organic compounds; energy
D) inorganic compounds; energy
E) carbon dioxide; carbon

Answer 3

B

Question 4

The enzyme catalase is used to detoxify which harmful oxygen species?

A) hydroxyl radical
B) superoxide
C) hydrogen peroxide
D) ozone
E) singlet oxygen

Question 5

What term applies to a microbe that can synthesize all of its cellular constituents from a simple carbon source and inorganic salts?

A) autotroph
B) heterotroph
C) auxotroph
D) prototroph
E) a chemotroph

Question 6

Term for microbes that grow optimally at very high salt concentrations.

A) osmolphiles
B) barophiles
C) halophiles
D) psychrophiles
E) thermophiles

Question 7

A lithotroph is defined as an organism that uses _____ as a source of _____.

A) inorganic compounds; energy and electrons
B) organic compounds; energy and electronss.
C) inorganic compounds; carbon
D) sunlight; energy
E) carbon dioxide; energy

Question 8

What is the most readily useable form of nitrogen by microorganisms?

A) dinitrogen
B) ammonium ion
C) nitrate
D) nitrite
E) nitric oxide

Question 9

Which one of the following elements is considered a microelement,usually required in minute amounts in microbiological media?

A) phosphate
B) potassium
C) iron
D) manganese
E) magnesium

Question 10

Term applied to microbes that grow optimally at temperatures below 15°C.

A) psychrophiles
B) barophiles
C) alkalophiles
D) mesophiles
E) halophiles

Question 11

What is the function of siderophores?

A) Transporting waste products out of the cell.
B) Binding iron for transport into the cell.
C) Binding glucose for transport into the cell.
D) Transporting proteins out of the cell.
E) Moving potassium into the cell for osmotic regulation.

Question 12

What is the term for microbes that grow optimally at a pH below 5.5?

A) alkalophiles
B) psychrophiles
C) halophiles
D) acidophiles
E) barophiles

Question 13

Enrichment media that contains starch as the sole carbon source is encouraging the growth of microbes that produce _____ .

A) glucose
B) the enzyme amylase
C) the enzyme cellulase
D) all twenty amino acids
E) all required vitamins

Question 14

What is the most abundant form of nitrogen in the biosphere?

A) ammonia
B) nitrate
C) nitrite
D) dinitrogen
E) nitrous oxide

Question 15

An autotroph is defined as an organism that uses _____ as a source of _____.

A) sunlight; energy
B) organic compounds; carbon
C) organic compounds; energy
D) inorganic compounds; energy
E) carbon dioxide; carbon

Question 16

Term that applies to a bacterium that has an absolute requirement of oxygen for growth..

A) aerobe
B) anaerobe
C) aerotolerant anaerobe
D) facultative anaerobe
E) facultative aerobe

Question 17

Term for a bacterium that does not use oxygen for growth,but will grow in the presence of oxygen.

A) aerobe
B) anaerobe
C) aerotolerant anaerobe
D) facultative anaerobe
E) facultative aerobe

Question 18

Term for microbes that grow optimally at a pH above 8.5.

A) acidophiles
B) alkalophiles
C) barophiles
D) psychrophiles
E) halophiles

Question 19

A phototroph is defined as an organism that uses _____ as a source of _____.

A) carbon dioxide; carbon
B) organic compounds; carbon
C) inorganic compounds; energy
D) sunlight; energy
E) organic compounds; energy

Question 20

What is the most common solidifying agent used in microbiological media?

A) gelatin
B) agar
C) alginate
D) silica
E) polyacrylamide

Question 21

Which method listed below will result in sterilization of an environmental water sample?

A) Boiling the sample for ten minutes.
B) Adding bleach to the sample.
C) Autoclaving the sample.
D) Heating the sample to 70°C for 30 minutes.
E) Microwaving the sample for 3 minutes.

Question 22

How long would it take a culture of E.coli with a starting cell density of 1 X 10⁵ cells/ ml to reach a cell density of 1 X 10⁸ cells/ml if it had a generation time of 30 minutes?

A) 3 hours
B) 4 hours
C) 5 hours
D) 6 hours
E) 7 hours

Question 23

Which is the best definition of an antiseptic?

A) A chemical agent that is applied to hospital equipment to kill or inhibit microbes.
B) A chemical agent that is applied to living tissue to kill and inhibit microbes.
C) An antibiotic that is applied to living tissue.
D) A physical agent that is used to sterilize hospital equipment.
E) A physical agent that is used on human tissue to inhibit microbial growth.

Question 24

Which of these methods can be used to obtain a viable cell count?

A) counting chamber direct count
B) turbidity measurement
C) plate counts of serial dilutions
D) loop dilution
E) optical density

Question 25

Alcohols like ethanol and isopropanol are commonly used as antiseptics because they are very effective at reducing the bacterial load.What is their mode of action?

A) disrupting the plasma membrane
B) inhibiting DNA replication
C) inhibiting protein synthesis
D) disruption of the peptidoglycan
E) inhibiting transcription

Question 26

The plate count method was used to estimate the number of bacteria in a culture over time.Serial dilutions were made of culture samples at various time points.A 0.1 ml portion of the 10⁻⁶ dilution was spread over the surface of a nutrient agar plate for each time point.The plates were incubated for 24 hrs and the colony forming units (CFU)were counted on each plate.A total of 45 colonies were counted on the plate for the 30 minute time point.What was the cell population for this time point?

A) 45 X 10⁴ CFU/ml
B) 45 X 10⁵ CFU/ml
C) 45 X 10⁶ CFU/ml
D) 45 X 10⁷ CFU/ml
E) 45 X 10⁸ CFU/ml

Question 27

If a cell culture contains 400 cells/ml at time = 0 and it has a generation time of 30 minutes,how many cells (cells/ml)will be present after 2 hours of incubation?

A) 1200 cells/ml
B) 1600 cells/ml
C) 2400 cells/ml
D) 3200 cells/ml
E) 6400 cells/ml

Question 28

Fresh media is inoculated with an actively growing Escherichia coli culture.You measure the optical density (OD)at the time of inoculation and record a value of 0.05)Two hours later you take another reading and record a optical density of 0.2)What is the generation time for your culture?

A) 30 minutes
B) 40 minutes
C) 50 minutes
D) 60 minutes
E) Cannot determine from the information given.

Question 29

During steady state growth in a chemostat,the growth rate of the cells is equivalent to:

A) the nutrient concentration.
B) the generation time.
C) the cell yield.
D) the flow rate.
E) the dilution rate.

Question 30

Prototrophic microbes need to be grown on a complex medium because they have several growth factor requirements.

Question 31

An autotroph is an organism that obtains its energy from the sun.

Question 32

A heterotroph is an organism that uses organic carbon as its carbon source.

Question 33

What is a chemostat?

A) A system used for the continuous culture of microbial cells.
B) A chemical used as a substrate for growth of microbial cells.
C) The maximum growth rate that can be obtained for a useable substrate.
D) A batch culture that uses a defined medium for growth.
E) A nutrient that is able to control the growth rate of a bacterial culture.

Question 34

Generation time is the average time it takes an actively growing cell in a population to divide.

Question 35

If you had an E.coli culture with a starting cell density of 1 X 10⁶ cells/ml and it had a generation time of 40 minutes,what would be the cell density after incubation for 6 hours?

A) 3 X 10⁸ cells/ml
B) 5.1 X 10⁸ cell/ml
C) 6.3 X 10⁸ cells/ml
D) 9.4 X 10⁸ cells/ml
E) 1 X 10⁹ cells/ml

Question 36

What would you use to measure the optical density of a bacterial culture?

A) a Petroff-Hauser counting chamber
B) a flow cytometer
C) the plate count method
D) a spectrophotometer
E) a microscope

Question 37

What is the mean growth rate for a culture that has a generation time of 1 hour?

A) 1 hr.
B) 2 hr.
C) 1 hr⁻¹.
D) 2 hr⁻¹.
E) Cannot determine from the information given.

Question 38

Many pharmaceutical products are heat sensitive so they are sterilized:

A) by ultraviolet radiation.
B) by ionizing radiation.
C) with ozone gas.
D) with chlorine gas.
E) by freezing.

Question 39

Many disinfectants are strong oxidizing agents and disrupt many cellular functions.Which of these is an example of an oxidizing agent?

A) isopropanol
B) carbolic acid
C) triclosan
D) chlorine bleach
E) phenol

Question 40

In order for a chemostat to operate properly,what must the reservoir contain?

A) a complex medium
B) vitamins
C) all twenty amino acids
D) a limiting nutrient
E) oxygen

Question 41

Compare and contrast sterilization to disinfection.Give an example for both.

Question 42

The use of a good antiseptic,such as Betadine,results in sterilization.

Question 43

What are the ingredients in MacConkey agar makes it both selective and differential? Give an example for its use.

Question 44

The process commonly used by the dairy industry to reduce the number of microbes in milk and destroy any pathogens that may be present is called ______________.

Question 45

The growth curve generated for a microbial batch culture consists of four phases.Explain what is happening to the culture during each of the phases.

Question 46

Would ionizing radiation be safe to use on food? Why?

Question 47

A microbe that grows optimally at a temperature below 15°C is called a __________.

Question 48

The bile salts in MacConkey agar,which inhibits the growth of many bacteria,make this media differential in nature.

Question 49

Pasteurization is a method of sterilization.

Question 50

A microbe that grows in the presence of oxygen but does not use oxygen for growth is called a(n)__________ __________.

Question 51

A device used for the continuous culturing of bacteria is called a _________.

Question 52

Nucleic acids strongly absorb _____________ radiation of 260 nm.

Question 53

Microbes that have an absolute requirement for oxygen are called obligate aerobes.